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Updated: Jul 18, 2026

10:42
Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
Published on: May 3, 2019
トンガ・ケルメデック島の下の融解の動態は,231Pa−235U体系から推論された
1Laboratoire de Geochimie et Cosmochimie, Institut de Physique du Globe de Paris-CNRS, UMR7579, 4 Place Jussieu, 75252 Paris Cedex 05, France. Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK.
まとめ
トンガ・ケルマデック・ラバのプロタクトニウム231とウラン235の比率を研究すると,流体添加と部分的な溶融の歴史が明らかになる. トンガの溶岩は6万年前の流体添加を示し,ケルメデックの溶岩は溶融効果が過剰に印刷されていることを示している.
科学分野:
- 地質化学 地質化学
- イソトープジオクロノロジー
- 火山学 火山学とは
背景:
- トンガ・ケルマデック島は,マントルの過程を研究するための天然の実験室です.
- プロタクトニウム231とウラン235の間のような放射性不均衡は,地質学的出来事の時間尺度に関する洞察を提供します.
研究 の 目的:
- トンガとケルマデック・アーク・ラバの流体添加と部分溶解のタイミングとメカニズムを区別する.
- マントルの源流程のトレーサーとして (231) Pa-(235) U 不均衡を活用する.
主な方法:
- トンガとケルメデック・アーチからのラバの231Pa~235U比の測定.
- サブダクションゾーン動態とマグマ生成の文脈における同位体データの解釈.
主要な成果:
- トンガの溶岩は231Pa/235U比 <1を示しており,これは約6万年前,潜水板からの流体添加と一致しています.
- Kermadecの溶岩は231Pa/235U比>1を示し,部分溶融プロセスが流体添加の効果を覆っていることを示しています.
結論:
- (231) Pa-(235) Uシステムは,弧の設定で,流体主導のマントル源と融解主導のマントル源を効果的に区別します.
- 島弧の溶岩は,流動岩相互作用と融解生成の複雑な歴史を記録し,弧の異なるセグメントで明確なサインを持っています.
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